The role of nonesterified fatty acids and of alpha 1-fetoprotein in estrogen-dependent endocrine systems.

We discuss the various experimental findings to date that indicate that AFP may be considered as a positive or negative modulator of estrogenic action. Moreover, we show that this protein, even when nonestrogenophilic, is able to bind other hydrophobic ligands, in particular nonesterified fatty acids. These fatty acids inhibit the binding of estrogens to murine AFP as well as to the cytosolic estrogen receptors. Thus, the AFPs of all species--whether or not estrogenophilic--might play an endocrinologic role through the intermediary of the unsaturated fatty acids to which they associate with high affinity.